Sorry, but you just can't save him from himself. Unless, as another poster up thread has said you are blunt with him. Or enlist the person you think could help.
When my mum died ten years ago, my Dad couldn't spend money fast enough. He will be 73 this year. A cruise with his lady friend (whom my self and another close relative suspect he was seeing before mum died). He spent money hand over fist on clothes for the cruise because said new lady friend was a snob.
He was insistent that she was going to sell her house, he was going to sell his house and they would live together in the new residence which they had purchased together. I think he thought he was going to live at her house in the interim. (Albeit she was a good source of information when telling my close relative that Dad was going to let the house to a couple with dubious intent. Whist I can't remember the details, it was basically a scam to get his house off him in the long run. He still believes this couple to be good friends, not least they were friends with both mum and dad. Close relative had to sit Dad down and calmly point out the pitfalls to the arrangement. Fortunately that put the kibosh on it. On being caught out all the dubious couple could say was, 'we don't want to fall out or have any bad feeling about this.') Another incident with this same couple when they asked Dad if he would lie in court to say he had been a witness to something he had not seen. My Dad refused. He does have some morals, not least perjury has a custodial sentence if found guilty. It's ok, he still believes these people to be his friends.
He described his father as easily led. Must run in the family.
It was only the fact that the lady friend was no more going to sell her house than fly in the air that stopped Dad putting his house on the market. The fact that she was married was beside the point, obviously. OK, in name only as her husband had left some years previously to live with his new partner. Lady friend would not agree to a divorce because she didn't want to lose half her assets when the house got sold.
A conservatory extension on Dad's house which cost seventeen grand. Installing a downstairs toilet (not in the conservatory may I add.)
Lady friend and close relative had to save him from himself once again when he was about to pay a 'doorstep cowboy' to do some work i.e. do you want your driveway tarmacked ? That sort of thing.
He spent five grand on a new roof because he decided the house needed it. All he could say is, 'it (the roof) goes back to Victorian times' No it doesn't. Those houses were built in the 1940's something like that. It was just another opportunity for me and a close relative to roll our eyes and think, 'it's your money.' It's not even if any of these, 'improvements' were even mentioned when mum was alive.
Eventually, when the financial slack was taken up, he half jokingly admitted to being poor. Then and only then did he decide to wind his neck in and start living back like when mum was alive i.e. living within their/his means. OK, my mum was allergic to spending because she was, like a lot of older people, scared of not having enough to live on after retirement. Her death meant he was out of control let off the leash and could do what he liked and thought he was emperor of the world.
For him, living within his means is both his pensions and whatever rental income he gets from his lodgers. He's on top of his bills and went on holiday at Christmas & New Year with this week's lady friend.
I don't believe he got an insurance pay-out when mum died either. He did get her share of their jointly owned house though.
As a close relative pointed out: Dad got married shortly after having to shave regularly. So all this finding his way with new relationships is foreign to him.
My husband remarked that he went straight from home to working for the armed forces as a teenager. (Couldn't leave home quick enough after falling out with his stepmother. His mum had died, his Dad remarried. So, maybe this behaviour was normal to him but unusual to my family.) The armed forces are a patriarchal organisation. He bought himself out of the army a couple of years after marrying my mum i.e. he went from being taken care of in his job to having a wife. She died, he was left to make his own decisions. Please see above.